1. Field of the Invention
The present invention relates to adaptive cruise control system and method for an automotive vehicle (hereinafter, also called a host vehicle) with an inter-vehicle distance control function to follow a preceding vehicle which is traveling ahead of the host vehicle.
2. Description of the Related Art
A Japanese Patent Application First Publication No. 2000-168395 published on Jun. 20, 2000 exemplifies a previously proposed adaptive cruise control system. In the previously proposed vehicular cruise control system disclosed in the above-identified Japanese Patent Application First Publication, an inter-vehicle distance between the host vehicle and the preceding vehicle is detected and a cruise speed run is carried out at a constant speed (so-called, a set cruise speed) which is set by a vehicular driver of the host vehicle. For example, [if] the preceding vehicle [becomes approached to] may approach the host vehicle or becomes spaced apart from the host vehicle so that the inter-vehicle distance is varied. At this time, the previously proposed vehicular adaptive cruise control system adjusts a braking force or a driving force of the host vehicle so that the inter-vehicle distance is made substantially equal to a target inter-vehicle distance. As described above, a vehicular running state is feedback controlled. In addition, in order to calculate the target inter-vehicle distance, for example, a traveling speed of the preceding vehicle is detected, is multiplied by an inter-vehicle time duration, and is added to a distance to make the host vehicle stop to calculate the target inter-vehicle distance.
It is noted that the inter-vehicle distance time duration is defined as a time duration required for the host vehicle to be reached to the present position of the preceding vehicle (in other words, a time required for the host vehicle to run by a distance corresponding to the inter-vehicle distance). For example, the inter-vehicle distance time duration is previously set as about two seconds. It is also noted that the distance to make the vehicle stop corresponds to a distance left between the host vehicle and the preceding vehicle when the host vehicle stops while the preceding vehicle is stopped and is preset to, for example, 2 meters. It is also noted that since when the host vehicle is running at the constant speed at a predetermined inter-vehicle distance, viz., the target inter-vehicle distance, the traveling speed of the preceding vehicle is exactly equal to or substantially equal to that of the host vehicle, the traveling speed of the host vehicle may be used to calculate the target inter-vehicle distance.